import numpy as np
import pandas as pd

arr = np.random.randint(1, 20, size=(3, 3))
df = pd.DataFrame(arr, columns=['c', 'b', 'a'])
print('原始数据: \n', df)
print('按行索引降序排序: \n', df.sort_index(ascending=False))
print('按列标签升序排序: \n', df.sort_index(axis=1))
